Material handling apparatus



Nov. 30, 1965 E. B. LONG 3,220580 MATERIA HANDLING APPARATUS Filed Feb.19, 1984 z sheets-sheet 1 Nov. 30, 1965 E. B. LoNG MATERIA HANDLING'APPARATUS 3 Sheets-Sheet 2 Filed Feb. 19, 1964 IN VEN TOR. ELTo/Y a/Y.

Nov. 30, 1965 E. B. LONG MATERIA HANDLING APPARATUS 3 Sheets-Sheet 5Filed Feb. 19, 1964 United States Patent O 3,220,580 MATERIA LENGAPPARATUS Elton B. Long, lurlington, Iowa, assignor to J. I. CaseCompany, Racine, Wis., a corporation of Wisconsin Filed Feb. 19, 1964,Ser. No. 346,021 9 Claims. (Cl. 214-140) This application is acontinuation-in-part of Long application Serial No. 257,538, filedFebruary ll, 1963, now abandoned, and assigned to the assignee of thepresent invention.

This invention relates to material handling equipment and, particularly,to a loader assembly secured to a prime mover such as a tractor thatincludes a pivotally mounted bucket disposed across the front end of thetractor. Such an assembly is generally referred to as a front endloader, in which the bucket position thereof is usually loaded by movingthe bucket into a pile of material, after which the lift arms may beraised and the tractor driven to a new location. At this point, thebucket is swung about the front end of the lift arms into a dumpingposition to discharge the contents, after which the tractor is drivenback for another load.

Earth moving equipment, such as tractor mounted front end loaders, towhich the present invention is directed, have been on the market forsome time. A typical loader assembly includes a pair of lift arms thatare pivotally mounted on a main frame fixedly securedto the tractor. Theinner ends of the lift arms are located adjacent the tractor operatorand the outer ends of the lift arms, when in the lowered position, aredisposed adjacent the ground between the tractor radiator and the frontWheels. The `bucket extends across the front of the tractor and ispivotally connected to the lower ends of the lift arms. The bucket ismoved between the digging, lifting and loading positions by ahydraulically operated linkage mechanism that is controlled by theoperator through a valve arrangement located adjacent the tractor seat.

Up until recently, loaders have been essentially manually Controlleddevices, which is to say that the positioning of the bucket through itsvarious positions depended entirely upon the control of the operator.Thus, the operator was depended upon to move and maintain the bucketlevel during movement thereof between the loaded and dumping positionsand to see to it that the bucket has been returned to the diggingposition before the tractor moves in to receive another load. Theplacing of this burden on the operator substantially reduced the speedat which he could operate and thus the amount of material that he couldmove in any given period. Furthermore, this also required a great dealof skill on the part of the operator in order to prevent spilling ofmaterial from the 'bucket during the lifting operation. The tendency tospill was due to the characteristic arcuate movement of the lift armsand bucket, during the raising movement in which the bucket is tiltedmore and more backwardly toward the tractor wherein the material isspilled over the rear edge, causing damage to the tractor and danger tothe operator. Attempts have been made to correct this diculty byintroducing the principle of the well known parallel motion linkage, orvariations thereof, in combination with the lift arms so that the bucketis held substantially in fixed ang'ular relation to the groundthroughout the raising movement. This, while it effectively avoidedspilling over the back edge of the bucket, induced spilling of the loadover the front edge or lip of the bucket, particularly at the beginningof the lifting movement which, although not particularly dangerous, wasinefiicient and undesira'ble.

Another factor limiting the speed at which the loader can be operated isthe one which requires that the opera- ICC tor take the time toaccurately reposition the bucket to take on a subsequent load after thepreceding one has been dumped. This has usually been accomplished by theoperator lining up a ,bucket position indicator located within full viewof the operator. Thus, it can be appreciated that if an apparatus wasfound which Would automatically level the bucket during the liftingoperation and then return the 'bucket to the digging position after thebucket has 'been dumped, then the operator would be almost completelyfree to concentrate on Operating the tractor at its maximum speed andobtain capacity leading.

In accordance with the present invention, there is provided a loadermechanism which incorporates a novel yet highly efficient hydraulicallyoperated self-leveling mechanism that will hold the bucket insubstantially fixed relation to the lift arms during the initial liftingmovement; but which will change this relation and maintain the bucketapproximately level, or at least in approxirnately fixed angularrelation to the ground during the remaining part of the upward movement,in spite of the swinging or arcuate upward movement of the lift arm. Inthis way, spilling of the load over the lip of the 'bucket during thefirst foot or two of lifting movement is greatly reduced, while spillingover the back edge is virtually eliminated during the rest of the upwardmovement. The mechanism includes a 'simple "slave cylinder that islinked hydraulically to the cylinders used for adjusting the position ofthe bucket. The slave cylinder is connected to the lift arms and goesinto action as the lift cylinder is actuated to level the bucket andprevent the spilling of material over the end walls of the bucket.

The novel loader assem'bly further includes a hydraulic control systemthat acts to automatically return the bucket to the digging positionafter the bucket has been dumped. This is accomplished by vautomaticallysupplying fluid under pressure to the bucket positioning cylinders toreposition the bucket to the digging position during the downwardmovement of the lift arms.

These and other advantages will be apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIGURE 1 is a plan view of a tractor with a loader mechanism mounted onthe |front end thereof;

FIGURE 2 is a right side elevation of the loader mechanism with partsbroken away and the bucket and associated control therefor illustratedin the digging and lifting positions and the hydraulic system shown indiagrammatic form;

FIGURE 3 is a left-side elevation of the loader mechanism similar toFIGURE 2;

FIGURE 4 is a view showing the positions taken by the bucket and bucketpositioning mechanism when the lift arms have just been raised ofi theground;

FIGURE 5 is a view similar to FIGURE 4 showing the lift arm, *bucket andassociated bucket linkage in the partially raised position;

FIGURE 6 is a view similar to FIGURE 5 showing in solid lines the liftarms and bucket in the fully raised position and in dotted lines thepositions of the various components after the 'bucket has been dumped;and

FIGURE 7 is a schematic diagram showing the hydraulic control system forthe loader.

The same reference numbers have been given to the same or similar partswherever they appear in the drawings and specification, and in the caseof FIGURE 3, the components corresponding to those shown in FIG- URE 2have been given the same number with a prime added thereto.

Referring first to FIGURE 1, there is shown a tractor 12 on which hasbeen mounted at the front end thereof a loader mechanism indicated bythe letter L. The loader mechanism includes a main frame structure 10that is attached to the tractor 1-2- by suitable fastening means. Theframe serves as the main support member and is generally U-shaped in theplan view in that it extends parallel to'the sides of the tractorforward of the operator and includes an inverted U-shaped section acrossthe front thereof. The frame 10 includes uprights or stanchions 14, 16spaced on opposite sides of the tractor 12, which stanchions areconnected to the transversely extending inverted U-shaped support 17 byforwardly extending braces 15,

The various details of the loader construction can be best seen byreferring to FIGURES 2 and 3. As shown in these figures, the loaderstructure consists of aV pair of lift arms or booms 18, 18' located onopposite sides of the tractor. The lift arms 18, 18' are pivotallyconnected to stanchions 14, 16, respectively, by pivot pins 22, 22'.Connected to the lower ends of the lift arms 18, 18' by means of pivotpins 24, 24', respectively, is the bucket 26. The lower` end of lift arm18 is located between brackets 42, 44 secured to bucket 26 and the pin24 extencls therethrough. The pin 24' extends through the lower end oflift arm 18' and bucket brackets 42', 44'.

The lift arms 18, 18' are pivoted about pins 22,` 22' by the operationof hydraulic cylinders 34, 34' through the extension or retraction ofpiston rods 32, 32' extendingl outwardly from cylinders 34, 34',respectively. The inner or lower ends of cylinders 34, 34' are connectedto stanchions 14, 16, respectively, by pins 36, 36'. The outer ends ofrods 32, 32' are disposed between and connected to pairs of downwardlyextending re-enforcing plates 28', 28' that are secured to anintermediate portion of the lift arms 18, 18', respectively. Thus, itcan be seen that when fiuid pressure is applied to the left-hand end ofcylinders 34, 34' (FIGURE 2), the lift arms 18, 18' are moved in acounterclockwise direction about pivot pins 22, 22' to raise the bucket26. Conversely, when fiuid is supplied to the opposite ends'of cylinders34, 34', the lift arms 18, 18' are moved in a' clockwise direction tolower the bucket 26.

The positioning of the bucket relative to pivot pins 24, 24' to move thebucket' between the digging, loading, and unloading positions isaccomplished by the hydraulically operated bucket poistioning mechanismshown in various positions in FIGURES 2 through 6. The hydraulicallyoperated bucket positioning mechanisms connected to each of the liftarms and at their opposite end to the bucket 26 are identical and thusonly the one disposed between lift arm 18 and brackets 42,` 44 will bedescribed in detail. The bucket positioning mechanism connected betweenlift' arm 18' and oppositely disposed brackets 42', 44' is illustratedin FIGURE 3, and the corresponding parts are appropriately numbered.

The bucket positioning mechanism consists of a link 38 that is securedbetween the upper portion of the brackets 42,` 44 by a pin 40. Theopposite end of the link 38 is connected by pin 46between a pair oflevers 48.' The levers 48 are in turn connectedat their opposite ends.to an intermediate portion of the lift arm 18 by pin 50. It can thus beseen that pivotal movement of the lever 48' about pin 50 will pivotbucket 26 in the same direction'about the end of lift arm 18. Toeifectuate movement of the linkage mechanism and through it bucket26, lafluid cylinder 54 is pinned to an intermediate portion of levers 48 by apivotal connection 52' which comprises a trunnion type support for thecylinder 54. The cylinder 54 has a piston rod 56 that extends forwardlyalong lift arm 18 and is pivotally connected at its end thereof to a lugor stop 60 by means of pin 58. Thus, introduction of pressure fiuid intoone end of the cylinder 54 and corresponding withdrawal of fiuid fromthe other end will result in axial movement of cylinder 54 which willcause pivotal movement of levers 48 and corresponding pivotal movementof bucket 26. It is, of course, understood that the two bucketpositioning mechanisms operate simultaneously to bring about the desiredresult.

For effecting control of the lift cylinders 34, 34' and bucket cylinders54, 54', a conventional or other suitable type of hydraulic system isemployed, and is conventionally illustrated as follows. A reservoir 62contains a supply of hydraulic fiuid which is pressurized andtransmitted by means of a pump 64 to a valve 66. A control lever 68 whenactuated in one direction admits fiuid to conduit 70 while allowingfiuid in conduit 72 to return through an exhaust conduit 74 to reservoir62. The conduit '70 leads to conduit 76, which in turn leads to theupper end of cylinders 54, 54'. The conduit 72 communicates with conduit78, which communicates with the lower end of cylinders 54, 54'. Theabove described manipulation of control 68 will therefore cause upwardmovement of cylinders 54, 54' and tilting of bucket 26, for example, forthe full line position of FIGURE 2 to the dotted or rolled-back positionthereof. This, of course, is the break-out action of the device, and itwill be noted that the larger capacity ends of the cylinders 54, 54.-'-those not encumbered by their corresponding piston rods are used in thebreak-out operation. Since this operation is the one which requires thegreatest development of force on the part of cylin-ders 54, 54', it is adecided advantage that the larger ends of these cylinders are utilizedin this break-out operation.

The manipulation of handle 68 in the opposite direction directs pressurefiuid through conduits 72 and 78 into the lower end of cylinders 54,54', where it` works on the limited area of pistons 80, 88' to causedownward movement of cylinders 54, 54'. The downward movement ofcylinders 54, 54' causes tilting of levers 48, 48', and bucket 26 in aclockwise direction and ultimately into the dotted position shown inFIGURE 6.

The valve 66 has another control lever 82 which when actuated in onedirection will direct pressure fiuid into conduit 84 which leads to thelower end of abovementioned lift cylinders 34, 34'. Such action willalso exhaust fiuid from a conduit 86 which leads from the right end ofcylinders 34, 34'. The pressure fluid will cause outward movement of thepiston rods 32, 32', and swinging of lift arms 18, 18' in acounterclockwise direcv tion about pivotal connections 22, 22', ashereinbefor'e suggested.

In the usual operation of a device of this kind, bucket 26 is placedapproximately in the full line position indicated in FIGURE 2, and thetractor is maneuvered into a position to force the bucket into a pile ofmaterial to be handled. Next, lever 68. is actuated in the properdirection to cause bucket 26 to be tilted or rolled back to the dottedposition in FIGURE 2. It, will be noted that, in this position, whichrepresents the extreme rearward position of the bucket, the. upper rim88 is tilted forwardly to some extent, which is undesirable sinceappreciable quantities of the load may spill if the tractor is drivenany distance with the bucket in this position. Accordingly, control 82is actuated to raise lift arms 18, 18' to some desired position fortraveling to the point of discharge. Such a position is shown in FIGURE4 in which the lift arms have been raised appreciably until rim 88 hasbecome essentially level. It is to be noted that links 38, 38' are stillin close proximity to stops 60, 60', if not actually in contacttherewith. In other words, bucket 26 has changed its relation to liftarms 18, 18', if at all, only a very small amount in moving from thedotted position in FIGURE 2 to the full line position in FIGURE 4.

Turning now' to FIGURE 5, it will be noted that the lift arms have beenraised substantially from the FIGURE 4 position. Rim 88, however, isstill level and this has been brought about by changing the relationbetween bucket 26 and lift arms 18, 18' substantially from that shown inFIGURES 2 and 4. This is brought about by the manipulation of cylinders54, 54' to the right to swing lever 48 in a clockwise direction. It isto be noted that links 38, 38' are now a substantial distance from stops60, 60'.

In FIGURE 6, lift arms 18, 18' have been swung still further upwardly toapproximately its maximum upward position. However, rim 88 is stilllevel by virtue of further movement to the right of cylinders 54, 54',in the manner just described. FIGURE 6 also shows the dumping positionof bucket 26, this being brought about by manipulation of control 68 andmovement of cylinders 54, 54' to the right a maximum amount, asindicated in dotted lines in FIGURE 6.

As will be apparent, in order to maintain the described control ofbucket 26, rather precise actuation of cylinders 54, 54' is requiredand, while this might be accomplished through control 68 by a highlyskilled operator, in the present instance it is accomplishedautomatically Without any attention on the part of the operator.

As discussed above, suitable provision must be made to change theposition of the bucket relative to the lift arms, when the lift arms arebeing rased, to prevent the material contained in the bucket fromspilling back over the operator. After the bucket has been loaded andmoved to an upright position by the operator, the normal tendency is forthe bucket to dip toward the operator during the upward movement of thelift arms. This is due to the fact that the lift arms and the bucketmove in an arcuate path due to their pivotal movement about pvot pins22, 22'.

In order to prevent the bucket from tipping out of the level position,provision must be made to move the bucket forward about pivot pins 24,24' an amount necessary to compensate for the backward tilting movementof the bucket during raising of the lift arms. To this end, the tiltingand attendant spilling is prevented by providing a novel hydraulicself-leveling mechanism which directs fiuid under pressure to thehydraulic bucket positioning cylinders to move the bucket forward apredetermined incremental amount, relative to the end of the lift arms,to compensate for the rearward bucket movement brought about by thearcuate travel of the lift arms.

The novel system in question includes a hydraulic slave cylinder 96 thathas one end thereof connected to the lower portion of stanchion 14 by apin 1430. Extending outwardly of the cylinder 96 is a piston rod 94 andattached piston 98 that is connected between a pair of rearwardlyextending brackets 90 secured to the lift arm 18 by a pin 92. Theopposite ends of the cylinder 96 are connected through suitablehydraulic lines 74, 76 to opposite ends of the cylinders 54, 54'. Inparticular, the head end of the cylinder 96 communicates with the headend of the cylinders 54, 54' through conduit 76 and the rod ends of thecylinders 96, 54, 54' are interconnected through conduit 78.

Briefiy, it will be seen that when the lift arrn 18 is rased, it carrieswith it the rod 94, which displaces fiuid from the rod end of thecylinder 96 through conduit 78 to the rod end of cylinders 54, 54' toeffectuate downward movement of the cylinders 54, 54' and clockwisemovement of levers 48 (FIGURE 2). This clock- Wise movement of levers 48will tend to tilt the bucket forwardly an amount calculated tocompensate for the tendency of the arcuate action of the lift arms tomove the bucket rearwardly and thus retain the bucket in the horizontalposition.

Briefiy, swingng motion of lift arms 18, 18' will eventually causemovement of piston 98 and a pumping action in cylinder 96. However, inthe position of the parts shown in FIGURE 2, such motion will beinsignificant or very slight, whereas as the lift arms swing upwardlyand piston rod 94 becomes more nearly tangent to the -arc described bythe lever arm represented by the distance between pivotal connections 22and 92, the motion will become greater until in the position of the liftarm shown in FIGURE 5 it is quite substantial. Since all of the severalcylinders and conduits are normally entirely full of fiuid, the motionsof piston 98 will be reflected in similar motions of cylinders 54, 54'and, therefore, without any manipulation of control 68, the upwardswinging of lift arm 18, through cylinder 96 will cause movement ofcylinders 54, 54' and shifting of the relation of bucket 26 to the liftarms. As Will be apparent, upward swinging of lift arm 18 will causedevelopment of pressure in the upper end of cylinder 96 which will betransmitted through conduit 78 to the lower end of cylinders 54, 54'.This will cause a certain amount of downward movement of cylinders 54,54', and relative tilting of bucket 26 in a clockwise direction.However, owing to the fact that lift arm 18 under these conditions isswinging in a counterclockwise direction, the result will generally beto maintain bucket 26 in a level position, and the dimensions ofcylinder 96 and cylinders 54, 54' are readily chosen so that theserelations will be obtained. The dimensions of cylinder 96 are chosen tosupply suflicient fiuid to actuate both cylinders 54, 54' the necessaryamount to maintain the bucket in the required position. However, it isundesirable to maintain bucket 26 in the dotted position of FIGURE 2,relative to the lift arms throughout the lifting movement, and it is forthis reason that cylinder 96 is so placed as to be in a substantiallydead center relation to pvot 22 when lift arm 18 is lowered. The initialmovement of lift arm 18 from the FIGURE 2 to the FIGURE 4 position,causes little, if any, pumping action in cylinder 96. Therefore, bucket26 is not shifted in relation to lift arms 18, 18' to any appreciableextent, at least, in its movement from the FIGURE 2 to the FIGURE 4position. However, after leaving the FIGURE 4 position, the pumpingaction of cylinder 96 will have increased to 'such an extent as tosupply sufiicient fluid to cylinders 54, 54' to maintain bucket 26substantially in a level position throughout the rest of the upwardmovement, even to the extreme position shown in FIGURE 6.

From this latter position, the bucket may be readily dumped by a simplemanipulation of control 68, which will feed the necessary fluid intoconduit 78 to cause movement of cylinders 54, 54' into the dottedposition of FIGURE 6, which will cause dumping of the bucket.

It can 'be -appreciated that since this 'novel hydraulically operatedself-leveling system operates independently of the operator, he is leftfree to perform his other duties, such as moving the tnactor to and fromthe pile being moved, and to perform any other functions that may berequired during the lifting action of the bucket.

After the bucket has been raised to its uppermost position and dumped(FIGURE 6), it must be subsequently moved to the position shown inFIGURE 2 to handle the next load. Prior to the instant invention, it hasbeen the oper'ator's job to take the time and effort to reposition thebucket, and even then it was necessary to provide him with some sort ofindioating means due to the lack of clear visibility.

In accordance with the instant invention, there is provided a novelhydraulic system that functions to automatically return the bucket tothe digging position from the dumped position as the lift anns are beinglowered. The details of this arrangement can best be seen by referringto FIGURES 3 and 7 which show the appanatus and hydraulic circuitryprovided for accornplishing this function.

Referng first to FIGURE 7, it is seen that there is illustrated inschematic form a conventional mech-anism for lifting and dumping thecylinders and the novel selfleveling mechanism referred to above. Inaddition, there is provided a return-to-dig slave cylinder 101 which isinterrelated to the bucket positioning or dump cylinders 54, 54' in 'amanner to be hereinafter described, but which in essence functions toposition the cylinders 54, 54' to return the bucket 26 to the diggingposition when the lift arms are lowered.

The cylinder 101 is positioned on the opposite side of the frame 10 fromcylinder 96 and is interconnected between 'stanchon 16 and lift arm 18'.As illustrated, the cylinder 101 includes a piston rod 102 that isconnected by pin 103 to a pair of brackets 105 secured to lift arm 18'.The cylinder housing is connected to stanchion 16 by pivot pin 107. Whenthe lift arm 18' is raised, the piston rod 102 connected to piston 104located in cylinder 101' is moved upward, 'as shown in FIGURE 3, and tothe right in FIGURE 7. The piston end of cylinder 101 is connectedthrough a first branch of conduit 106 and anti-cavitation check valve108 to the reservoir 62 and through a second branch of conduit 106 andcheck valve 110 to conduit 76 leading to the piston end of bucketpositionng cylinders 54, 54'. The rod end of cylinder 101 is directlyconnected to reservoir 62, which thus makes cylinder 101 a single actingcylinder. The anticavitation check valve 108 permits the flow of fiuidfrom reservoir 62 into the piston end of cylinder 101 during the outwardor suckiing movement of piston 104 and prevents the backflow of fiuid inconduit 106 from returning to reservoir 62 during the pressure stroke ofpiston 104. Similarly, the check valve 110 permits fluid to fiow intoconduit 76 during the pressure stroke of piston 104 and prevents thebackflow of fiuid in conduit 106 from conduit 76 during the suckingstroke of piston 104.

The opposite or rod ends of bucket positioning cylinders 54, 54' are incommunication with conduit 72 connected to which there is an inlinerelief valve 114. Other relief valves, not shown, are also providedwherever necessary to relieve Iany undesirable build-up of pressureoccurring during the openation of the loader. The relief valve 114provides for an escape of fiuid from the conduits 72, 78 leading fromtherod ends of bucket positioning cylinders 54, 54' to permit movement ofcylinders 54, 54' to the left when they are subjected to fluid underpressure through conduit 106 and check valve 110. The cylinder 101 isdesigned to provide fiuid under pressure to cylinders 54, 54' which,when combined with the fiuid forced out of cylinder 96 by the inwardmovement of piston rod 94, will move cylinders 54, 54' the distancenecessary to return the bucket to the digging position. The fiuid forcedout of the rod ends of cylinders 54, 54' minus the fluid that flows intothe rod end of cylinder 96 will force open relief valve 114 and returnto reservoir 62.

The aforementioned hydraulic system functions to automatically returnthe bucket to the flat level position at the ground line when the liftarms are (lowered. Briefly stated, during the raising of lift arms 18,18', the piston rod 102,:is moved outwardly of thecylinder 101, whichresults in oil being sucked through the anti-cavitation check valve 108.When the lift arms reach the full lift position, the piston side ofpiston 101 is full of oil. Also, at the same time, piston rod 94 movesoutwardly and the piston side of cylinder 96 is filled with fiuid. Thebucket is then dumped by iactuation of the dump control valve 'and thevalve controlling the operation of lift cylinders 34, 34' is. positionedto return the lift arms to` their lowered position. As the lift armslower, the piston rod 102 moves into cylinder 101 which forces the oiltrapped in the'piston end of cylinder 101 out. through conduit 106, pastcheck valve 110, into conduit 76 and the piston end of cylinders 54,54', and inward moveme'nt of piston rod 94 forces fiuid out of cylinder96 into conduit 76. The introduction of this fiuid into the cylinders54, 54' builds up the pressure therein to move the cylinders 54, 54' tothe left, as shown in FIGURE 7, an amount suficient to retum the bucketto the diggi'ng position when the lift arms have reached ground level.During this portion of the cycle, the oil in the rod end of the bucketpositioning cylinders 54, 54' is pressurized to a point whereit reachesan inline relief pressure that opens reIiefvalVe 114 to return theexcess oil in conduits 72, 78 to the reservoir. After the lift armsreach the ground line, the bucket has been returned to the diggingposition since the total volume of oil that has been pumped out of thecylinders 101 and` 96' equals'the correct volume needed for thecylin'-ders 54, 54' to move them the correct amount of stroke required toreposition the bucket to a digging attitude.

While the return-to-dig hydraulic system has been disclosed inconjunction with a hydraulic self-leveling arrangement, it is, ofcourse, obvious that if desired such arrangement` could be -used withloaders that have mechanical self-leveling, or no self-leveling systemof any kind, since the return-to-dig arrangement can operate completelyindependent therefrom. In this situation, the cylinder 101 would 'bedesigned so that it pumped into conduit 76 that 'amount of fiuidnecessary to move the bucket positioning cylinders the distancenecessary to move the bucket to the digging position when the lift armsare lowered.

The method of operation of the entire system illustrated in the drawingscan best be seen by referring to FIGURE 7 and is summan'zed as follows:

The Operating sequence will be set forth beginning with the bucket inthe digging position and will be carried through the loading, lifting,self-leveling, dumping and return-to-dig stages.

After the bucket is loaded, the control valve 66 is operated to move thebucket positoni-ng cylinders 54, 54-' and bucket to the position shownin dotted lines in FIG- URE 2. Fluid is then directed 'through conduit84 to the piston ends of lift cylinders 34, 34' to raise the lift arms18, 18' to move the bucket -to the dumping position. During this upwardmovement of the lift arms, lthe piston rod 94 of cylinder 96 is movedoutwardly to pump fiuid through conduit 74 to the rod end of cylinders54, 54' to -move the bucket clockwise (IFIGURE 2) to compensate for thearcuate movement of the lift arms and thus maintain the bucket level andprevent spilling. The fiuid forced out of the piston ends of thecylinders 54, 54' is I simultaneously returned to the piston end ofself-leveling cylinder end 96 through conduit 76. Also, during theraising of the lift arms, the piston rod '102 is moved out of cylinder101, which draws fiuid from the reservoir 62 through conduit 106 pastcheck valve 108 into the piston end of cylinder 101.

When the lift arms have reached their maximum raised positions and thetractor is properly positioned, the bucket is dumped by introducingfiuid to the rod end of cylinders '54, 54'. When the dumping has beencompleted, -the lift arms are again lowered by suitable operation oflift cylinders 34, 34'. When this occurs, the. piston rod 102 is moved'to the left (or down by lift arm 18'), which forces fiuid from thepiston end of cylinder 101 past check. valve 1'10 -into the piston endsof cylinders 54, 54'. At the same time, the piston rod 94 ofself-levelng cylinder 96 is moved in the same direction as rod 1102which forced fiuid. out of cylinder 96 into conduit 76. The amount offiuid forced into the piston ends of cylinders 54, 54' is calculated tobe sufiicient to move the cylinders and associated linkages the:distance necessary to move the bucket to the return-to-dig positionwhen the lift arms reach ground level.

While a particular embodiment has been disclosed, many changes andsubstitutions of equivalents can be made without departing from thescope of the invention. It is, of course, intended to cover by theappended claims all such modifications that fall within the true spiritand scope of the invention.

I claim:

1. A' front end loader for a'tractor lincluding a frame adapted to besecured to said tractor, a pair of transversely spaced lift armspivotally mounted at one end thereof to said frame, a bucket pivotallymounted to the opposite ends of said lift arms, hydraulic means disposedbetween the frame and one of said lift arms for raising and loweringsaid lift arms, a bucket positioning'means dis'- posed between at leastone of said lift arms and said bucket and including la double actinghydraulic cylinder for moving 'the bucket between the digging anddumping positions, a first slave' cylinder assembly 'interconnectedbetween said frame and one of said lift arms, means for supplying fluidto one side of said first slave cylinder during the raising of said liftarms, means for directing fluid 'from said one side of said first slavecylinder to one side 'of said bucket cylinder during the loweringmovement of said lift arms, a second double acting slave cylinderassembly interconnected between said frame and the other of said liftarms, means for directing fluid from one side of said second slavecylinder to the other side of said bucket positioning cylinders tomaintain the bucket level during raising of said lift arms and means fordirecting fluid from the other side of said second slave cylinder tosa-id one side of said bucket cylinder during lowering of said 'liftarms, 'the bucket cylinder and slave cylinders being so designed thatthe fluid 'supplied from said slave cylinders to said bucket cylinderduring lowering movement of the lift arms will effect movement of 1thebucket positioning means to return the bucket to the digging positionwhen the lift arms return to ground level.

2. A front end loader for a tractor including a main frame, a pair oftransversely spaced klift arms pivotally mounted at one end thereof tosaid frame, a bucket pivotally mounted to the opposite ends of said liftar'ms, hydraulic means disposed between the frame and each of said lift-arms for raising and lowering said lift arms, a bucket positioningmeans disposed between each of said lift -arms and said bucket includinga double acting hydraulic cylinder for moving the bucket between thedigging and dumping positions, a first slave cylinder assemblyinterconnected between said frame and one of said lift arms, areservoir, means for directing fluid from said reservoir to one side ofsaid first slave cylinder during the raising of said lift arms, a checkvalve in said last mentioned means for preventing the flow of fluid fromsaid first slave cylinder to said reservoir during lowering of said liftarms, conduit means interconnecting said one side of said -first slavecylinder and one side of both of said bucket cylinders during thelower-ing of said lift arms, a check valve in said last conduit meansfor preventing fluid from fiowing to said one side of said first slavecylinder from said bucket cylinders during lifting of said lift arms, asecond double acting slave cylinder assembly interconnected between saidframe and the other of said lift arms, means for directing fluid fromone side of 'said second slave cylinder to the other side of said bucketpositioning cylinders to maintain the 'bucket level during raising ofsaid lift arms and means for directing fluid from the other side of saidsecond slave cylinder to said one side of said bucket cylinders duringlowering of said lift arms, the bucket cylinders and slave cylindersbeing so designed that the fluid flow from said slave cylinders to saidbucket cylinders during lowering movement of 'the 'lift arms will efiectmovement of the bucket positioning means to return the bucket to thedigging position when the lift arms return to ground level, and valvemeans for relieving the fluid from said one side of said bucketcylinders during said lowering movement.

3. A front end loader for a tractor including a frame adapted to besecured to the tractor, a pair of transversely spaced lift armspivotally mounted at one end thereof to said frame, a bucket pivotallymounted to the opposite ends of said lift arms, lifting means disposedbetween the frame and each of said lift arms for raising and loweringsaid lift arms, a bucket positioning means disposed between each of saidlift arms and said bucket including a lever linkage assembly and adouble acting hydraulic cylinder including a piston end and a rod endfor moving the bucket between the digging and dumping positions uponactuation of said cylinder, a first slave cylinder assembly including acylinder element connected to said frame and a piston rod connected toone of said lift arms, a reservoir, means for directing fluid from saidreservoir to the piston side of said first slave cylinder during theraising of said lift arms, a check valve in said last-mentioned meansfor preventing the return of fluid from the piston side of said firstslave cylinder to said reservoir during lowering of said lift arms,conduit means interconnecting the piston side of said first slavecylinder and the piston end of each of said bucket cylinders during thelowering of said lift arms, a check valve in said conduit means forpreventing fluid from fiowing to the piston side of said first slavecylinder from the piston end of said bucket cylinders during lifting ofsaid lift arms, a second double acting slave cylinder assembly includinga cylinder element connected to said frame and a piston rod secured tothe other of said lift arms, means for directing fluid from the rod sideof said second slave cylinder to the rod end of said bucket positioningcylinders to maintain the bucket level during raising of said lift armsand means for directing fluid from the piston side of said second slavecylinder to the piston end of said bucket cylinders during lowering ofsaid lift arms, the bucket cylinders and slave cylinders being sodesigned that the fluid flow from said slave cylinders to said bucketcylinders during lowering movement of the lift arms and associatedpiston rods will effect movement of the bucket positioning means toreturn the bucket to the digging position when the lift arms return toground level,, and relief valve means for venting the rod ends of thebucket positioning cylinders during the lowering movement of said liftarms.

4. A material handling device including a frame, a pair of lift armspivotally mounted to the frame adjacent one end thereof, a transverselyextending bucket pivotally mounted to the opposite ends of said liftarms, lifting means disposed between said frame and at least one of saidlift arms to pivot same relative to said frame, bucket positioning meansdisposed between an intermediate portion of at least one of said liftarms and said bucket, said bucket positioning means comprising ahydraulically operated linkage mechanism including a lever assemblypivotally connected at one end thereof to an intermediate portion ofsaid one lift arm, a link interconnecting the opposite end of said leverassembly to a portion of said bucket spaced from said one lift arm and acylinder assembly secured to an intermediate section of said leverassembly, said cylinder assembly including a cylinder trunnion mountedto said lever assembly and a piston rod fixedly connected to said liftarm adjacent the bucket end thereof, whereby upon introduction of fluidto the large end of said cylinder the bucket will be moved into anupwardly extending position, a self-leveling slave cylinder assemblymounted between said frame and one of said lift arms adjacent thepivotal connection between said lselected lift arm and frame wherebysaid slave cylinder will be positioned in accordance with the movementof said aforementioned lift arm, and conduit means interconnecting saidself-leveling cylinder and bucket positioning cylinder whereby fluidwill be pumped to the rod end of the cylinder to maintain the bucketsubstantially level during upward movement of the lift arms.

5. A material handling device including a frame, a pair of lift armspivotally mounted to the frame at one end of each of said arms, atransversely eXtending bucket pivotally mounted to the other end of eachof said lift arms, lifting means disposed between said frame and atleast one of said lift arms to pivot same relative to the frame, bucketpositioning means disposed between an intermediate portion of at leastone of said lift arms and said bucket and including a linkage mechanismcontrolled by a hydraulic cylinder, a bucket self-leveling cylinderassembly mounted between said frame and one of said lift arms adjacentthe pivotal connection between said one lift arm and frame including acylinder element and a rod element, means pivotally securing saidcylinder and rod elements to the lift arm and frame, said last mentionedmeans being disposed in substantial alignment with the pivotalconnection between said one lift arm and frame when the lift arms are intheir lowermost position, and conduit means linterconnecting saidself-leveling cylinder and bucket positioning cylinder whereby When thebucket is rolled back the lift arm may be raised sufficiently to levelthe bucket without appreciable effect on the bucket from the hydraulicself-leveling cylinder but upon further up- Ward movement of the liftarms the self-leveling cylinder will be .regulated to direct fluid tothe hydraulic cylinder to maintain the bucket substantially level andthus prevent spilling thereof.

6. A material handling device including a frame, a pair of lift armspivotally mounted to the frame adjacent one end thereof, a transverselyextending bucket pivotally mounted to the opposite ends of said liftarms, a bucket stop member secured to said lift arms adjacent said opposite ends, hydraulically operated lifting means disposed between saidframe and each of said lift arms to pivot them relative to said frame,bucket positioning means disposed between an intermediate portion ofeach of said lift arms and said bucket, said bucket positioning meansincluding a hydraulically operated linkage mechanism including a leverassembly pivotally connected at one end thereof to an intermediateportion of its respective lift arms, a link interconnecting the oppositeend of said lever assembly to a portion of said bucket spaced from saidlift arm and a cylinder assembly secured to an intermediate section ofsaid lever assembly, said cylinder assembly including a cylinder elementtrunnion mounted to said lever assembly' and a piston rod fixedlysecured to said stop member, whereby upon introduction of fluid to thepiston end of said cylinder the bucket will be moved upwardly relativeto the ends of said lift arms and when fluid is directed to the rod endof the cylinder the bucket will be moved in the opposite direction, aself-leveling slave cylinder assembly pivotally mounted between saidframe and one of said lift arms and including a piston rod secured tosaid one lift arm and a cylinder element secured to said frame, andconduit means interconnectinng said self-leveling cylinder and bucketpositioning cylinders whereby when the lift arms are raised fluid willbe supplied from the rod end of said slave cylinder to the rod end ofsaid bucket positioning cylinders to automatically maintain the bucketlevel and prevent spilling therefrom 7. A front end loader for a tractorincluding a frame adapted to be secured to said tractor, a pair oftransversely spaced lift arms pivotally mounted at one end thereof tosaid frame, a bucket pivotally mounted to the opposite ends of said liftarms, hydraulic means disposed between the frame and one of said liftarms for raising and lowering said lift arms, a bucket positioning meansdisposed between at least one of said lift arms and said bucket andincluding a hydraulic cylinder for moving the bucket between the diggingand dumping positions, a slave cylinder assembly interconnected betweensaid frame and one of said lift arms, means for supplying fluid to oneside of said slave cylinder during the raising of the lift arms, meansfor directing fluid from said one side of said slave cylinder to saidlbucket positioning cylinder during the lowering movement of said liftarms, the bucket cylinder and slave cylinder being constructed andarranged so that the fluid supplied from said slave cylinder to saidbucket cylinder during lowering movement of the lift arms will effectmovement of the bucket positioning means to automatically return theVbucket to the digging position when the lift arms are returned to groundlevel.

8. A front end loader for a tractor including a frame adapted to besecured to said tractor, a pair of lift arms located on opposite sidesof the tractor and pivotally mounted at one end thereof to said frame, abucket pivotally mounted to the opposite ends of said lift arms,hydraulic means disposed between the frame and one of said lift arms forraising and lowering the lift arms, a bucket positioning means disposedbetween at least one of said lift arms and said bucket and adapted toposition said bucket relative to said lift arms, said bucket positioningmeans including a hydraulic cylinder for moving the bucket between thedigging and dumping positions, a slave cylinder assembly interconnectedbetween said frame and one of said lift arms adjacent the pivotalconnection of said one lift arm and frame, a fluid filled reservoir,conduit means interconnecting said reservoir and slave cylinder, a checkvalve in said conduit means permitting fluid to flow from said reservoirto said slave cylinder during upward movement of said lift arms, andconduit means leading from said slave cylinder to said bucket cylinderwhereby fluid is directed from said slave cylinder to said bucketpositioning cylinder during the lowering movement of said lift arrns toactuate the bucket positioning means to automatically return the bucketto the digging position when the lift arms are returned to ground level.

9. A front end loader for a tractor including a frame, a pair of liftarms pivotally secured at one of their ends to said frame, lifting meansdisposed between said frame and said lift arms to pivot same relative tosaid frame, a bucket pivotally mounted to the opposite ends of said liftarms, a bucket positioning means disposed between each of said lift armsand said bucket and adapted to position the bucket relative to said liftarms, said bucket positioning means including a double acting hydrauliccylinder for moving the bucket between the digging and dumpingpositions, a slave cylinder assembly including a piston rod secured toone of said lift arms adjacent the pivotal connection between said liftarm and said frame, and a cylinder element secured to said frame member,a fluid filled reservoir, conduit means interconnecting the reservoirand piston end of said cylinder element, a check valve in said conduitmeans permitting fluid to flow from said reservoir to the piston end ofsaid slave cylinder during upward movement of said lift arms, conduitmeans leading from said slave cylinder to one side of said bucketcylinders whereby fluid is directed from said slave cylinder to saidbucket cylinders during the lowering movement of said lift arms toposition said cylinders to automatically return the bucket to thedigging position when the lift arms are returned to ground level, reliefvalve means for venting the other side of said bucket positioningcylinders during downward movement of said lift arms, and check valvemeans in said last mentioned conduit means for preventing the backflowof fluid into the piston end of said slave cylinder during upwardmovement of said lift arms.

References Cited by the Examiner UNITED STATES PATENTS 2,731,162 1/1956Walstrom 214fl- 2,782,946 2/1957 Hough 214- 140 2,860,793 11/1958Lapsley 214-140 2,881,931 4/1959 Mackie 214-140 2,990,072 6/ 1961Mindrum 214--140 3, 140,001 7/ 1964 Stroder 214-140 HUGO O. SCHULZ,Primary Examiner.

1. A FRONT END LOADER FOR A TRACTOR INCLUDING A FRAME ADAPTED TO BE SECURED TO SAID TRACTOR, A PAIR OF TRANSVERSELY SPACED LIFT ARMS PIVOTALLY MOUNTED AT ONE END THEREOF TO SAID FRAME, A BUCKET PIVOTALLY MOUNTED TO THE OPPOSITE ENDS OF SAID LIFT ARMS, HYRAULIC MEANS DISPOSED BETEWEEN THE FRAME AND ONE OF SAID LIFT ARMS FOR RAISING AND LOWERING SAID LIFT ARMS, A BUCKET POSITIONINE MEANS DISPOSED BETWEEN AT LEAST ONE OF SAID LIFT ARMS AND SAID BUCKET AND INCLUDING A DOUBLE ACTING HYDRAULIC CYLINER FOR MOVING THE BUCKET BETWEEN THE DIGGING AND DUMPING POSITIONS, A FIRST SLAVE CYLINDER ASSEMBLY INTERCONNECTED POSITIONS, A FIRST SLAVE CYLINDER ASSEMBLY INTERCONNECTED SUPPLY FLUID TO ONE SIDE OF SAID FIRST SLAVE CYLINDER DURING THE RAISING OF SAID LIFT ARMS, MEANS FO DIRECTING FLUID FROM SAID ONE SIDE OF SAID FIRST SLAVE CYLINDER TO ONE SIDE OF SAID BUCKET CYLINDER DURING THE LOWERING MOVEMENT OF SAID LIFT ARMS, A SECOND DOUBLE ACTING SLAVE CYLINDER ASSEMBLY INTERCONNECTED BETWEEN SAID FRAME AND THE OTHER OF AID LIFT ARMS, MEANS FOR DIRECTING FLUID FROM ONE SIDE OF SAID SECOND SLVE CYLINDER TO THE OTHER SIDE OF SAID BUCKET POSITIONING CYLINDERS TO MAINTAIN THE BUCKET LEVEL DURING RAISING OF SAID LIFT ARMS AND MEANS FOR DIRECTING FLUID FROM THE OTHER SIDE OF SAID SECOND SLAVE CYLINDER TO SAID ONE SIDE OF SAID BUCKET CYLINDER DURING LOWERING OF SAID LIFT ARMS, THE BUCKET CYLINDER AND SLAVE CYLINDERS BEING SO DESIGNED THAT THE FLUID SUPPLIED FROM SAID SLAVE CYLINDERS TO SAID BUCKET CYLINDER DURING LOWERING MOVEMENT OF THE LIFT ARMS WILL EFFECT MOVEMENT OF THE BUCKET POSITIONING MEANS TO RETURN THE BUCKET TO THE DIGGING POSITION WHEN THE LIFT ARMS RETURN TO GROUND LEVEL. 